# 统计英文文本字母频率
def A(a):
    # 转换为小写并过滤非字母字符
    b = [char.lower() for char in a if char.isalpha()]
    # 统计频率
    c = {}
    for char in b:
        c[char] = c.get(char, 0) + 1
    return c

a = "Hello, World!"
b = A(a)
print("字母频率统计:", b)